1. Technical Field
Several aspects of the present invention relate to a recording method for recording a desired exposure pattern in a holographic mask having a recording layer, a holographic exposure method for exposing a photosensitive material film on a substrate to light by using the holographic mask so that a desired exposure pattern is printed on the photosensitive material film, a method for manufacturing a semiconductor device and a method for manufacturing an electro-optic device.
2. Related Art
In photolithography technologies to form an electric circuit or element on a substrate such as a wafer for use in a semiconductor device and the like, attention has been focused on a holographic exposure method that allows a fine pattern to be printed.
The holographic exposure method is a method in which a recording layer of a holographic mask is illuminated with a light beam for reconstruction and the diffracted light is caused by an interference pattern that has been recorded in advance as a hologram in the recording layer.
A photosensitive material film on a substrate is exposed to the diffracted light so that a desired exposure pattern is printed onto the film.
The method is described in “0.05 μm Enabling Lithography for Low-Temperature Polysilicon Displays” SID 2003 Digest, pages 350-353.
The foregoing holographic exposure method has higher resolution than general exposure methods that use lens optical systems.
On the other hand, the foregoing method has such characteristics that the numerical aperture is less adjustable and the focal depth is smaller than the lens optical systems.
Therefore, the method has a problem in that if a device such as a semiconductor device is formed on a surface of a substrate, exposure need be performed a plurality of times (multiple exposure) with the gap between a holographic mask and the substrate being changed to be adapted for unevenness of the surface, that is unevenness of a photosensitive material film.
In order to solve this problem, various devices have been known in related art.
These devices include an exposure device including a light source that irradiates a film to be exposed on a substrate with exposure light, a positioning mechanism that positions an exposure master plate in the optical path of the exposure light, a driving mechanism that controls the distance between the exposure master plate and the film to be exposed, and a scanning mechanism that changes the position of the exposure light relative to the film to be exposed (WO03/010803, pages 4 and 13, FIG. 8).
In the foregoing exposure device, a distance measurement device that measures the distance between the exposure master plane and the film to be exposed is included, and based on the measured result by this distance measurement device, the driving mechanism controls the distance between the exposure master plane and the film to be exposed.
More specifically, in the exposure process, the exposure light is emitted so as to scan the film to be exposed through the exposure master plate.
In synchronization with this scan, the driving mechanism controls the gap between the exposure master plate and the film to be exposed to have a desired distance by moving a stage with a substrate mounted thereon in the Z-axis direction.
Therefore, exposure is performed with the focal position of exposure light being periodically changed in accordance with changes of the height of the surface of the film to be exposed.
This is intended to overcome the small focal depth, one of the problems in the holographic exposure method.
In methods using the foregoing exposure device of related art, if the substrate to be exposed is made larger in size, the stage is also required to be larger in size.
With the size increasing, the inertial mass of the stage increases.
As a result, errors are likely to be greater in periodically controlling the focal point of exposure light by the foregoing driving mechanism.
Thus, there exists a problem in that the focal position of the exposure light does not follow unevenness of the surface of the film to be exposed and undulations of the substrate, so that part of the substrate to be exposed might remain unexposed to light.
Further, regarding the case where relatively high resolution is not required but a large focal depth is desired, a technique of easily adjusting the focal depth has not been developed in the holographic exposure method using a holographic mask.